gmail_reader.py

from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
import pickle
import os.path

class GMailReader:
    def __init__(self):
        print('User Created')
        self.scopes = ['https://www.googleapis.com/auth/gmail.readonly']
        creds = None
        if os.path.exists('token-readonly.pickle'):
            with open('token-readonly.pickle', 'rb') as token:
                creds = pickle.load(token)
        try:
            if not creds or not creds.valid:
                if creds and creds.expired and creds.refresh_token:
                    creds.refresh(Request())
                else:
                    flow = InstalledAppFlow.from_client_secrets_file(
                        'credentials.json', self.scopes)
                    creds = flow.run_local_server(port=0)
                    with open('token-readonly.pickle', 'wb') as token:
                        pickle.dump(creds, token)
            self.service = build('gmail', 'v1', credentials=creds)
        except Exception as error:
            print("Error occured while authenticating :-")
            print(error)
        print('GMail API auth completed')

    def get_messages(self, query, **kwargs): 
        # an optional argument of length is provided to determine maximum number of results to retrieve
        try:
            obj = self.service.users().messages().list(userId='me', q=query, maxResults=kwargs.get('length', None)).execute()
            print('%s messages retrieved matching the given query.' % len(obj['messages']))
            return obj['messages']
        except Exception as error:
            print('Error occurred while searching :- %s' % error)
            return None

    def get_single_message(self, query):
        message = self.get_messages(query, length=1)
        if not message:
            print('No messages matching the given query were found')
        else:
            messageid = message[0]['id']
            try:
                message = self.service.users().messages().get(userId='me', id=messageid, format='raw').execute()
                print('Message retrieved')
                return message
            except Exception as error:
                print('Error occurred while searching single message :- %s' % error)
                return None